Ultrasonic waves are used for inspecting the inner parts of the human body or animal or for measuring in a non-destructive manner the thickness or inside combinations of solid matter such as metal or plastic. In these cases, ultrasonic waves are realized in the form of probe (hereinafter, referred to as ‘ultrasonic probe’) for easy handling by users.
This ultrasonic probe has a structure in which a piezoelectric ceramic is formed on a rear block, a multi-layered acoustic matching layer is formed on the piezoelectric layer, and an acoustic lens is formed on the acoustic matching layer. Therefore, among ultrasonic waves generated from the piezoelectric ceramic, ultrasonic waves propagated toward the rear block are absorbed into the rear block, and ultrasonic waves propagated toward the acoustic matching layer are delivered to an inspection target through the acoustic matching layer and the acoustic lens.
Since in such a conventional ultrasonic probe the ultrasonic waves propagated toward the rear block are absorbed into the rear block, there is a limit to an increase in signal strength of ultrasonic waves propagated through the acoustic lens. Additionally, the ultrasonic waves propagated through the acoustic lens have a narrow bandwidth, which invites poor waveform characteristics.